clear all
R = 120;        %сопротивление  о_О О_О О_о
C = 33e-12;     %емкость        x_X X_X X_x
tau = R*C;      %тау         
shag = tau/100;
fprintf('tau =%f ns',tau*1e9);
T = shag;
t = 0:T:3*tau;
U(1) = 0;
S = 10;
for k=2:length(t);
    U(k) = (S+(tau/T)*U(k-1))/(1+tau/T);
end
plot(t,U)